Improved process for the manufacture of paper-stock



UNITED STATES PATENT OFFICE,

JOEL TIFFANY, OF ALBANY, NEW YORK.

Specification forming part of LettcrsPatent No. 56,832, dated July 31, 1866.

To all whom it may concern.-

Be it known that I, J OEL. TIFFANY, of the city and county of Albany, and State of New 7 York, have invented a new and improved process for preparing straw and other fibrous substances for the manufacture of paper or other articles of manufacture by converting said straw, 860., into pulp, of which the following is a specification.

There have been many different processes in use having the same object in view, which were only partially successful because of inherent defects in them, causing a large expenditure of means and time to accomplish a very imperfect result.

The end to be accomplished in the preparation of such material for the manufacture of paper is to produce a perfect separation of the fibers from each. other by dissolving the material that. holds them together in such a manner as to produce as little destructive effect upon the fiber itself as. possible.

To accomplish this purpose strong caustic alkaline liquors have been in use at boiling and higher degrees of temperature. The result has been, in such cases, that there has been a large waste of alkali, and also of stock treated, by the destruction of a portion of the fiber first brought into contact with the alkali,

so that, compared with the results obtained, the.

process has been too expensive, besides producing an inferior quality of pulp, making a harsh and brittle paper.

One class of processes in use for the reduction of paper-stock is that of boiling the stock in a caustic alkaline liquor in a close vessel and at a high temperature, indicated by an internal pressure of sixtyto one hundred and fifty pounds to the square inch. It has been found that under such treatment straw stock can be reduced to a pulpy condition in a'much less time and much more thoroughly than when boiled in open vessels but by such process there is a large consumption of time in getting up andthen in reducing the temperature,

taking from five to six hours to reduce the stock to a proper condition and have it ready for washing and use. Besides there is also a waste in the alkali used, by reason of the excessive action on and destruction of a portion of the stock treated, converting it into a pasty state, in which the alkali'is neutralized andthe stock destroyed. Again, there is a great.

waste of the stock treated by this process; be-

ing thus reduced to apasty state, it is carried off during the process of washing. Again, there is a great expenditure of fuel required in raising and keeping up the temperature of the mass at that indicated by sixty to one hundred and fifty poundsto the square inch, when.

no such temperature is valuable except as hereinafter stated.

A temperature much above boiling-heat is unnecessary to secure the speedy reduction of stock where the alkaline solution is brought into immediate contactwith every part of the stock treated. The particular benefit derived from temperature indicated by steam-pressure of sixty pounds and upward to the square inch is to be found in the pressure obtained, rather thanlin the temperature by which it is obtained.

The stock treated is tilled with small pores or cells, into which the alkaline solution cannot enter so as to come in contact with the inner portions of the stock unless forced therein by pressure. This. is accomplished by the pressure obtained by high temperature in close vessels, but at very great expense of time, fuel, alkali, and stock. The same pressure can be obtained by a much more speedy and cheaper process, and producing a much better result. This has been accomplished by forcing water into the vessel, thereby producing hydrostatic pressure upon the stock and forcing the liquid into every pore and cell in the same; but this process is found to be objectionable in that it necessarily dilutes the liquor used by the quantity of Water injected into the boiler to produce the pressure, and consequently requires the liquor in use originally in the boiler to be of a greater strength than necessary to reduce the stock, or to be of a strength too feeble to accomplish the reduction after it is thus diluted;

besides, the use of a larger quantity of caustic liquor than is necessary for the reduction of the stock renders also necessary the employment of more fuel and time .to produce and keep up the proper temperature.

As the end to be accomplished is to produce a perfect separation of the fibers of the stock from each other with as little destructive effect upon the same as possible, it is important to use an alkaline solution of as low a degree of strength as will accomplish such result, because a higher degree of strength tends to injure the fiber and results in a waste both of chemicals and stock. Therefore the action upon everypart of the stock should be simultaneous. This is obtained by producing the necessary pressure at the commencement by external mechanical means. I accomplish this result by pneumatic pressure; and my process is substantially as follows: I use an ordinary closed iron vessel or boiler such as the common rotary or stationary boilers in common use for boiling stock for makingpaper-pulp under high pressure. I charge the boiler in the manner well known to the art and trade of preparing paper-stock from straw for the man ufacture of paper. I prepare the caustic alkali in the usual manner known to the art or trade of preparing paper-stock by the use of a pure caustic alkali. I take an alkaline solution thus prepared, at a temperature of at least two hundred and twelve degrees (212) Fahrenheit, and of a quantity sufficient to cover the stock to be treated, and I inject the same into the boiler or vessel in the manner usually employed by persons boilin g. straw in close vessels for the manufacture of paper, so that in the charging of the boiler with the stock to be treated and with the liquor for treating the same, and in the preparation of the stock for treatment and of the liquor for treating it, the process is substantially the same as that now in general use by manufacturers of paper-pulp from straw and other fibrous material, to which reference is hereby made. a

My process differs from all other processes in this: After the vessel is properly charged with the stock and caustic liquor, and is closed air or steam tight, I immediately subject the contents thereof to any degree of pressure desirable by the injection of air by means of an air pump or pumps. In this way I force the canstic liquor into imme -te contact with every part of the stock to? reated, so that the action of the caustic liquor upon the stock in every part of the same is simultaneous, and consequently uniform, producing a speedy and uniform result in the disintegration of every part of the stock being treated, so that I am obliged to use no extra quantity of the liquor to obtain the pressure, and consequently no extra quantity of alkali. No part of the stock is acted upon more than the other, and a speedy and uniform result is obtained with a great saving of alkali, of stock, of fuel, and of time, in all reducing the expense of treating stock for the manufacture of paper-pulp' jfrom thirty to fifty per cent. over and above all other processes. We

The strength of the caustic alkali I use is from 1 to 2 Baum. I obtain a heat of from two hundred and twelve degrees (212) Fahrenheit to any point above, and maintain it for about three hours, in the method usually practiced by those engaged in boiling paper-stock. A temperature very little above that of boiling is sufficient.

Having thus fully described my invention and improvement, in connection with other processes of treating and reducing straw and other fibrous substances to a pulpy condition for the manufacture of paper, so that any one skilled in the art or trade to which this improvement most nearly relates can put the same into practical operation and use, I will proceed to state my claims.

I do not claim the use of a pure caustic alkali of any degree of strength or under any particular degree of pressure in the reduction of straw or other fibrous substances to a pulpy condition for the manufacture vof paper, nor do I claim the use of any particular degree of temperature in such process; but

What I do claim as my invention, and seek to secure by Letters Patent, is

1. The employment of pressure obtained by forcing into the vessel containing the stock to to be treated air, cold or hot, so as to obtain any degree of pressure necessary to force the caustic liquor into contact with every part of the stock, in combination with the caustic liquor so used, substantially in the manner and for the purpose above set forth and described.

2. The use of condensed cold air forced into the vessel containing stock, producing the necessary internal pressure upon the stock by heating and expanding the air within the vessel, in combination with the caustic liquor so used, substantially in the manner and for the purpose above set forth and described.

JOEL TIFFANY.

Witnesses J os. F. WINNE, EDWARD WADE. 

